34-2 Early Pliocene Drawdown And Expansion Of The Antarctic Peninsula Ice Sheet In Marguerite Bay

Session: High latitude paleoceanographic discoveries from Scientific Ocean Drilling (IODP, ODP, DSDP). (Posters)

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The George VI Land Ice Shelf is the second largest on the Antarctic Peninsula and the most vulnerable to climate change of all large ice shelves in Antarctica. Today it buttresses outlet glaciers on the southwestern margin of the Antarctic Peninsula Ice Sheet (APIS) slowing ice discharge into Marguerite Bay. While the ice shelf disappeared and grew back under early Holocene climate variation, its behavior under warmer conditions similar to Earth’s future is poorly constrained. Here we present new sedimentological and geochemical data from legacy Ocean Drilling Program Site 1097 within an updated chronology and show that George VI Ice Shelf was absent at ~5.2 to 4.9 Ma. Ice retreat in the earliest Pliocene was synchronous with that reconstructed at other sites along the West Antarctic Pacific margin and coincided with an increase in the strength of the Antarctic Circumpolar Current. A change in sediment provenance at Site 1097 suggests that the APIS began to dominate ice drainage into Marguerite Bay ~4.5 Ma with the sedimentology of the deposits pointing to a subpolar, meltwater-intensive glacial system before ~4.3 Ma. In contrast, a massive and stratified diamictite-dominated section younger than ~4.3 Ma, shows characteristics similar to Pleistocene deposits from the Marguerite Ice Stream Trough and occurs within a seismic unit showing progradation at the outer shelf. These changes in sedimentary systems reflect the response of the terrestrial Antarctic Peninsula Ice Sheet system to enhanced accumulation and retreat phases under Pliocene peak warming, and stable marine ice-sheet growth upon cooling.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2, 2026

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